1. FIELD OF THE INVENTION
This invention most generally relates to a heat exchanging device for heating a fluid such as air and is more particularly concerned with providing heated air by conduction of heat from a combustion passage to a first fluid passage which is enveloped by the combustion passage and conduction of heat to a second fluid passage surrounding the combustion passage. The combustion passage is substantially coextensive withbut is not in air mixing communication with the two fluid passages. The gases of combustion travel substantially in a helical path through the combustion passage. Even more particularly the invention relates to a heat exchanging device for heating air wherein the combustion region is defined by two concentric cylindrically configured heat exchange surfaces and the combustion chamber has an arcuate surface upon which a flame strikes along chordal paths of a circle having centers along the center line of the cylindrical outer shell.
2. DESCRIPTION OF THE PRIOR ART
It would be desirable and advantageous to have a heat exchange device which would be capable of burning waste oil products efficiently and in a manner which would allow easy cleaning of the burner unit and the heat exchanger.It would also be desireable to have a unit or device which has the combustion take place within the heat exchanger instead of in a chamber removed from the heat exchange region. It is also important that the combustion flame not impinge directly onto a surface causing the deposition of deposits or the incomplete and inefficient burning of the fuel which may result. It is also important that the gases of combustion be kept separate and in a non mixing relationship and that these hot combustion gases be directed in such a manner as to encounter large surfaces which are in thermal contact which the medium, such as air or water, which is to be heated.
It would also be desirable to position the burner unit or device within the heat exchanger in such a manner that the residual heat within the combustion chamber and heat stored within the refractory does not radiate back toward the burner unit. That is it is important that after combustion ceases the location of the flame introducing means or system, such as the nozzle of an oil burner unit, be in a relatively cool location.
In order to be able to burn waste oil products in an efficient and ecologically sound manner, it is critical that the combustion efficiency be within well defined specifications. It is required that the efficiency be not less than 75% as measured according to industry accepted standards of testing and that the residuals emitted be as completely oxidized as possible at this efficiency level, in particular, the design of a device for the burning (rapid oxidation) of contaminated waste oils should have, for purposes of maximum overall efficiency i.e., maintenance labor, combustion, heat exchange, etc., a smooth uniform, constant, controlled flow of combusted gases throughout and there should be no abrupt direction changes prior to exhausting of the gases. This is necessary to uniformly deposit, within the device those noncombustibles inherently generated by this process. When this is accomplished the heat exchange degradation process is more nearly uniform preventing premature heat exchange loss in any given area. The instant invention accomplishes such an objective. Applicant is not aware of any heat exchanger devices or assemblies presently available which meet the necessary criteria for the proper and effective burning of waste oil products coupled with the ability to expose completely and in total all prime heating surfaces for necessary, periodical inspection and/or mechanical cleaning. Nor is Applicant aware of a device which incorporates all of these desireable features within the relatively small volumetric configuration possible with this invention. Because of the unique combination of the arcuate heating surface of the combustion chamber of the present invention and the location of the burner unit with the associated nozzles, the region containing the burner unit nozzle will be the coolest after combustion ceases. This phenomena is due at least in part to the fact that the heat of radiation emanating from the combustion chamber will radiate at right angles to chords of the arcuate surface and the heat will thus radiate into the region defined by the quadrant diagonally opposite the quadrant defining the combustion chamber of the present invention. In fact Applicant is unaware of any such units available which have the advantages and characteristics described that burn regular fuels such as heating oil and/or gas.
Some inventions related to the instant invention and disclosed in the following United States Patents have been studied. The following is a brief description and discussion of these related inventions.
Juhnke, U.S. Pat. No. 2,056,465 discloses a heater having a cylindrical shape and including a plurality of passageways for air flow therethrough, the passageways allowing contact with the combustion gases in a middle cylinder defined by the inner cylinder wall and an outer wall, the outer wall also in contact with the air and the combustion gases.
Tate, U.S. Pat. No. 483, 819 discloses a hot air furnace which includes a central air passageway which contacts a middle cylinder containing the gases of combustion. The outer wall of the middle cylinder are also in contact with the air, providing two heated air masses.
Rice, U.S. Pat. No. 586,062 discloses a hot air furnace which includes a central jacket having a plurality of pipes having the shpe of the frustum of a cone. These pipes and the outer wall of the jacket radiate heat to the air masses outside the central jacket.
Muckelrath, U.S. Pat. No. 3,388,697 discloses an enlarged air heater for discharging large volumes of heated air toward outdoor work areas and the like comprising upper and lower tubular members within which bypassing non-communicating combustion and air passages are defined for progressively heating the air from the intake end to the discharge thereof. The combustion passage includes a fire tube and an exhaust chamber while the air passage includes a preheating chamber generally coextensive with the exhaust chamber an a final heating chamber generally coextensive with the fire tube.
Whitaker, U.S. Pat. No. 2,494,113 discloses improvements in furnaces used for the heating of buildings. In particular Whitaker teaches the introduction of the flame on a chord, i.e. the flame enters tangentially. He also discusses the notion of providing a spiral baffle plate which in effect directs the gases of combustion in a helical path around a plurality of four or more flues. The air to be heated eners the flues from an intake manifold passes through the flues being heated by the combustion gases and then passes into a hot air manifold at the top of the furnace for distrubtion by conventional means to the spaces to be heated.
Hoesman, U.S. Pat. No. 764,191 discloses a spiral draft configuration. The combustion gases are conveyed through pipes having a spiral arrangement. The spiral arrangement of the pipes induces a spiral draft, which he contends as being very effective in keeping up a rapid combustion. The air being heated ascends through the casing and the coiled pipes and is thoroughly and quickly heat by the hot combustion gases.